Method of reducing the width of cracks in masonry

ABSTRACT

The invention relates to a method to reduce the width of cracks that may be induced in masonry. The reinforcement strips comprise at least two straight, substantially parallel reinforcement wires connected to each other by means of a wire connecting structure. The reinforcement wires have a design yield strength f yd  equal or higher than 550/γ s  N/mm 2  and an equivalent diameter d equal or lower than 4 mm. The reinforcement strips have a resistance F against loads applied on said reinforcement strip and a design value of resistance F d . The reinforcement strip embedded in said joint has a bond capacity F bok  and a design bond capacity F bod . The design yield strength f yd  and the diameter d of said reinforcement wires are chosen so that the design value F d  of the reinforcement strip is equal or lower than the design bond capacity F bod  of the reinforcement strip.

TECHNICAL FIELD

This invention relates to a method of reducing the width of cracks thatmay be induced in masonry reinforced with reinforcement strips.

The invention further relates to a strip for the reinforcement ofmasonry.

BACKGROUND ART

Strips for the reinforcement of masonry are known in the art.

Masonry has a high compressive strength but a limited tensile strength.This leads to cracking when tensile and/or shear stresses develop. Byreinforcing masonry with strips, the risk of cracking is substantiallyreduced.

Although reinforcement strips having longitudinal wires having a highyield strength are existing, up to now calculation in design are donewith the much lower design yield strength. Using a higher design yieldstrength is of high importance as this may lead to a reduction in thecross-section of the longitudinal wires. A reduction of thecross-section of the longitudinal wires not only result in a reductionof the amount of steel required but also in a reduction of the minimumrequired thickness of a mortar joint.

However it is not meaningful to simply increase the design yieldstrength of the longitudinal wires of a reinforcement strip. Increasingthe design yield strength of the longitudinal wires has a directinfluence on the width of cracks induced in masonry as a higher tensilestress in the longitudinal wires will result in an increase of the widthof cracks that may be induced in the masonry.

To reduce the width of cracks it is common in the art to reduce thedesign stress in the steel, and thus increase the steel section of thereinforcement strip for a specific design load. Typically, a designyield strength of 435 MPa is used.

DISCLOSURE OF INVENTION

It is an object of the present invention to provide a method to reducethe width of cracks induced in masonry reinforced with reinforcementstrips using longitudinal wires having a high design yield strength.

It is another object of the present invention to provide a strip for thereinforcement of masonry avoiding the drawbacks of the prior art.

According to a first aspect of the present invention a method to reducethe width of cracks that may be induced in masonry is provided. Themasonry comprises layers of bricks and joints, preferably mortar joints.

The method according to the present invention comprises the step ofreinforcing at least one joint with reinforcement strips.

The reinforcement strips comprise at least two straight, substantiallyparallel reinforcement wires connected to each other by means of a wireconnecting structure. The reinforcements wires are preferably connectedto each other by welding a wire connecting structure between twoadjacent reinforcement wires, for example by welding the wire connectingstructure on mutually facing sides of the two reinforcement wires,alternately on the first reinforcement wire and the second reinforcementwire. The reinforcement wires are preferably steel wires. The wireconnecting structure is preferably made of steel.

The reinforcement wires have a yield strength f_(y) and a design yieldstrength f_(yd).

The design yield strength f_(yd) corresponds with the yield strengthf_(y) divided by safety factor γ_(s). The reinforcement wires of thereinforcement strip according to the present invention have a designyield strength f_(yd) equal or higher than 550/γ_(s) N/mm², morepreferably a design yield strength f_(yd) equal or higher than 600/γ_(s)N/mm². The safety factor γ_(s) is a partial factor for a materialproperty (steel), taking uncertainties in the material into account. Thesafety factor γ_(s) is for example equal to 1.15.

The reinforcement wires preferably have an equivalent diameter lowerthan 4 mm, more preferably lower than 3.80 mm for example 3.65 mm.

The reinforcement strip will provide a resistance F to the loadsapplied. The resistance F of the reinforcement strips to loads appliedis equal to the cross-sectional area of the reinforcement strip intension A_(s) multiplied by the yield strength f_(y) of thereinforcement wires:

F=A _(s) *f _(y).

The design value of the resistance of the reinforcement strip to loadsapplied is called F_(d). The design value of the resistance of thereinforcement strip to loads applied, F_(d) is equal to thecross-sectional area of the reinforcement strip in tension A_(s)multiplied by the design yield strength f_(yd) of the reinforcementwires:

F _(d) =A _(s) *f _(yd).

The reinforcement strip once embedded in a mortar joint has a bondcapacity F_(bok)(=characteristic bond capacity). The bond capacityF_(bok) of a reinforcement strip in masonry can be determined byEuropean Standard EN846-2. In the test of this European Standard a stripis embedded in mortar in a small wall of bonded masonry units. The stripis then subjected to tension in order to determine its bond strength.The reinforcement strip has a design value of the bond capacity F_(bod)also called design bond capacity. The design bond capacity F_(bod) isdefined as the bond capacity F_(bok) divided by a safety factor γ_(s′),i.e. F_(bok/γ) _(s′).

The safety factor γ_(s′) is a partial factor for a material (steelreinforcement) including uncertainties about geometry and modeling.γ_(s′ is typically ranging between) 1.7 and 2.7

According to the present invention the design yield strength f_(yd) ofthe reinforcement wires and the equivalent diameter d of thereinforcement wires are chosen in such a way that the design value ofthe resistance of a reinforcement strip to loads applied F_(d) is equalor lower than the design bond capacity F_(bod) of the reinforcementstrip without increasing the width of crack possibly induced in themasonry.

For a person skilled in the art it is clear that the design value of theresistance of a reinforcement strip to loads applied F_(d) has to beequal or higher than the design load E_(d).

The bond capacity F_(bok) (=characteristic bond capacity) of areinforcement strip and thus also the design bond capacity F_(bod) of areinforcement strip can be increased by increasing the anchorage lengthof a reinforcement strip and/or by increasing the lap length of twoneighbouring reinforcement strips.

However, in practice the anchorage length of a reinforcement strip islimited by the design of the reinforcement strip. More particularly, thewire connecting structure limits the lap length of two neighbouringreinforcement strips.

When overlapping neighbouring reinforcement strips, the reinforcementstrips should be put next to each other and preferably not on top ofeach other, otherwise the mortar will not cover the reinforcement stripsufficiently and the thickness of the joint will be increased. Apreferred method of overlapping reinforcement strips is by sliding oneend of a second reinforcement strip in one end of a first reinforcementstrip in such a way that the reinforcement wires of the neighbouringreinforcement strips remain in one plane and the first reinforcementwire of the first strip is thereby adjacent to the first wire of thesecond reinforcement strip and the second reinforcement wire of thefirst reinforcement strip is adjacent to the second wire reinforcementwire of the second reinforcement strip. The lap length of twoneighbouring reinforcement strips is limited by the design of thereinforcement strip, more particularly by the wire connecting structure.

In order to avoid pull out of reinforcement strip, the design yieldstrength f_(yd) and the equivalent diameter of the reinforcement wires dhave to be chosen in such a way that the design value of the resistanceof a reinforcement strip to loads applied F_(d) is equal or lower thanthe design bond capacity F_(bod) of the reinforcement strip in themortar over the anchorage length of the reinforcement strip.

As explained above, the anchorage length is limited by the design of thereinforcement strip.

This means that in case reinforcement wires of a specific equivalentdiameter are used having a design yield strength f_(yd) higher thanallowed by the bond capacity F_(bod) of the reinforcement strip, theequivalent diameter of the reinforcement wires should be reduced tobalance the design value of the resistance of a reinforcement stripF_(d) with the bond capacity F_(bod) and thus to avoid pull out over theprovided anchorage length.

However, by using reinforcement wires having a higher design yieldstrength f_(yd) and a reduced equivalent diameter d other concerns ariseas using such reinforcement wires may lead to an increase in the widthof cracks that may be induced in masonry.

According to Hooke's law an increase in the stress in the reinforcementwires will result in an increase in strain:

ε=E*σ

-   -   with ε: strain        -   E: Young's modulus        -   σ: tensile stress

A crack is induced in a masonry cross-section when the local tensilestrength of the masonry is exceeded. Once a crack is induced in themasonry, the tensile loads are taken by the reinforcement strip. Theload at the crack is then further transmitted from the reinforcementstrip to the mortar, more particularly from the reinforcement wires ofthe reinforcement strip to the mortar, over a length called the loadinglength l_(a) of the reinforcement strip or more particularly the loadinglength of the reinforcement wires of the reinforcement strip. At the endof the loading length, the strain in the steel is equal to the strain inthe masonry.

The width of a crack is related to the loading length and the strain ofthe reinforcement strip at the crack. The width of a crack can bederived from the following formula:

w=2*l _(a)*ε_(crack)

-   -   with w: width of a crack in the masonry;        -   l_(a): loading length of reinforcement strip;        -   ε_(crack): strain of the reinforcement strip caused by the        -   tensile stress σ_(crack) determined by the load in the crack

This means that by using reinforcement wires having a high design yieldstrength f_(yd), the strain in the reinforcement strip is increased. Asthe strain in the reinforcement wires is increased, the width of thecrack will increase unless the loading length is sufficiently reduced.

To avoid this problem the reinforcement wires of the reinforcement stripaccording to the present invention are provided with a plurality ofribs. By providing the reinforcement wires with ribs, the loading lengthcan be reduced.

The method according to the present invention allows using reinforcementstrips having high tensile reinforcement wires without increasing thewidth of cracks induced in masonry.

The reinforcement wires are preferably steel wires. In particularembodiments the steel comprises stainless steel.

Possibly, the steel wires are coated, for example with a zinc or zincalloy coating or with a polymer coating.

The reinforcement wires may have any type of cross-section. Preferredreinforcement wires have a circular cross-section, a rectangular or asquare cross-section.

The reinforcement wires are preferably drawn wires, although wires madeof sheet material and profiled wire can also be considered.

The equivalent diameter of the reinforcement wires is preferably equalor lower than 4 mm, for example 3.65 mm, 3.5 mm, 3.2 mm or 3 mm.

The wire connecting structure preferably comprises a wire having anequivalent diameter ranging between 2 and 4 mm. Preferably the wire is asteel wire.

In a preferred embodiment the reinforcement strips the wire connectingstructure is provided with protuberances protruding from the planecomprising said at least two straight reinforcement wires. Theprotuberances of the wire connecting structure form a spacing elementwhich keep the at least two straight reinforcement wires at a specificdistance form the layer of bricks below or from the layer of bricksabove or from both the layer of bricks below and above in order toguarantee the embedment of the reinforcing wires in the mortar.

The mortar can be applied before the laying of the reinforcement strips,after the laying of the reinforcement strips or before and after thelayer of the reinforcement strips.

The advantage of providing the wire connecting structure withprotuberances protruding from the plane comprising the at least tworeinforcement wires allows the complete embedment of the reinforcementwires in mortar. By using a reinforcement strip having a wire connectingstructure provided with protuberances, the thickness of the joint, moreparticularly the mortar joint is higher than the “thickness” of thereinforcement strip. With thickness of the reinforcement strip is meantthe height or depth of the protuberances of the wire connectingstructure or the sum or the height of dept of the protuberances of thewire connecting structure and the diameter of the reinforcement wires.

A further advantage of using reinforcement strip having a wireconnecting structure provided with protuberances is that as thereinforcement wires are completely embedded in the mortar layer, loadsinduced at a crack are transmitted over the shortest possible loadinglength from the reinforcement strip to the mortar.

Furthermore, the reinforcement wires will not be weakened by anydeformation and maintain their full tensile strength along their wholelength.

This preferred type of reinforcement strips allows masons at a buildingsite to use the following way of operation: applying firstly areinforcement strip on the upper side of the last laid layer of bricksfollowed by applying a mortar layer before the next layer of bricks isapplied. This way of operation offers serious advantages compared to therecommended way of operation comprising the steps of: applying firstly amortar layer on the upper surface of the last laid layer of bricks, thenapplying the reinforcement strip, finally applying another mortar layeron the reinforcement strip before the next layer of bricks is applied.The usually recommended way of operation is a cumbersome operation.

Any type of protuberances can be considered. The protuberances may forexample be provided by bending the wire connecting structure.Alternatively, the protuberances may be obtained by providing the wireconnecting structure with clips, such as plastic clips.

The protuberances may be provided at one side of the plane comprisingthe reinforcement wires, for example at the upper side or at the lowerside. Alternatively, the protuberances are provided at both sides of theplane comprising the reinforcement wires, i.e. at the upper and at thelower side.

The bent protuberances of the wire connecting structure may have anyform as for example a sinusoidal form.

In a preferred embodiment, the protuberances of the wire connectingstructure are located close to the reinforcement wires, e.g. within adistance of maximum 10 cm from the connecting points between the wireconnecting structure and the reinforcement wires, e.g. within a distanceof maximum 8 cm, e.g. of maximum 5 cm, e.g. of maximum 3 cm. Thisembodiment is particular advantageous for reinforcement strips to beused to reinforce walls where the bricks have hollow spaces inside. Incase the spacing elements are located in the middle of the wireconnecting structure, the protuberances risk to fall inside the hollowspaces and to miss completely their spacing function.

According to a second aspect of the present invention a reinforcementstrip adapted for the reinforcement of masonry is provided.

The reinforcement strip comprises reinforcement at least two straight,substantially parallel reinforcement wires connected to each other bymeans of a wire connecting structure. Preferably, the reinforcementstrip comprises two straight, substantially parallel steel reinforcementwires. The wire connecting structure is preferably made of steel.

The reinforcement wires have a yield strength f_(y) and a design yieldstrength f_(yd).

The reinforcement wires of the reinforcement strip according to thepresent invention have a design yield strength f_(yd) equal or higherthan 550/γ_(s) N/mm², more preferably a design yield strength f_(yd)equal or higher than 600/γ_(s) N/mm². The safety factor γ_(s) is forexample equal to 1.15.

The Reinforcement

The reinforcement wires preferably have an equivalent diameter lowerthan 4 mm, more preferably lower than 3.80 mm for example 3.65 mm. Thereinforcement wires are provided with a plurality of ribs.

According to a third aspect of the present invention masonry reinforcedwith the above described reinforcement strips is provided.

BRIEF DESCRIPTION OF FIGURES IN THE DRAWINGS

The invention will now be described into more detail with reference tothe accompanying drawings where

FIG. 1 shows a first embodiment of a reinforcement strip according tothe present invention;

FIG. 2 shows a second embodiment of a reinforcement strip according tothe present invention;

FIG. 3 shows a perspective view of a part of masonry comprising twolayers of bricks and an intermediate mortar joint, reinforced with areinforcement strip as shown in FIG. 2;

FIG. 4 shows a cross-section of the embodiment of FIG. 3;

FIG. 5 shows a cross-section similar to FIG. 4, but with another type ofreinforcement strip;

FIG. 6 shows a cross-section similar to FIG. 4 and FIG. 5 but with stillanother form of the reinforcement strip;

FIG. 7 a and FIG. 7 b shows a particular embodiment of a ladder type ofreinforcement strip;

FIG. 8 a, FIG. 8 b and FIG. 8 c illustrate reinforcing strips accordingto the invention whereby the protuberances of the wire connectingstructure are located close to the reinforcement wires.

MODE(S) FOR CARRYING OUT THE INVENTION

The present invention will be described with respect to particularembodiments and with reference to certain drawings but the invention isnot limited thereto but only by the claims. The drawings described areonly schematic and are non-limiting. In the drawings, the size of someof the elements may be exaggerated and not drawn on scale forillustrative purposes. The dimensions and the relative dimensions do notcorrespond to actual reductions to practice of the invention.

The following terms are provided solely to aid in the understanding ofthe inventions.

Masonry: all building systems that are constructed by stackingrelatively small units of stone, clay, or concrete, joined by forexample mortar or glue into the form of walls, columns, arches, beams ordomes;

Tensile strength: the maximum stress a material withstands whensubjected to an applied load. The value of the tensile strengthcorresponds with the load at failure divided by the originalcross-sectional area;

Yield strength: the stress at which a material begins to deformplastically;

Stress: the ratio of applied load to the cross-sectional area of anelement in tension;

Strain: a measure of the deformation of the material;

Equivalent diameter of a wire: the diameter of an imaginary wire havinga circular radial cross-section, which cross-section has a surfaceidentical to the surface area of the particular wire.

FIG. 1 describes a reinforcement strip 100 comprising two straight,substantially parallel steel reinforcement wires 102 welded to eachother by means of a steel wire connecting structure 104.

The wire connecting structure 104 of the embodiment shown in FIG. 1 runsbetween the two reinforcement wires 102 along a substantially zig-zagline. Such a wire reinforcement strip is called a truss type.

Ladder type reinforcement strips having as wire connecting structure aseries of cross members as described in U.S. Pat. No. 2,929,238 and U.S.Pat. No. 6,629,393 can also be considered.

The reinforcement wires 102 are steel wires having a yield strengthf_(y) equal or higher than 550 N/mm². More preferably, the reinforcementwires 102 have a yield strength f_(y) higher than 600 N/mm².

The reinforcement wires 102 have a design yield strength f_(yd). Thedesign yield strength f_(yd) of the reinforcement wires 102 is equal orhigher than 550/γ_(s) N/mm². More preferably the design yield strengthf_(yd) of the reinforcement wires 102 is equal or higher than 600/γ_(s)N/mm².

The reinforcement wires 102 have an equivalent diameter d equal or lowerthan 4 mm. In the embodiment shown in FIG. 1 the reinforcement wires 102are wires having a circular cross-section having a diameter of 3.65 mm.

The reinforcement wires 102 are provided with a plurality of ribs 106.

The reinforcement strip 100 has a resistance F against loads applied onthe reinforcement strip. The resistance F has a design value F_(d) equalto the cross-sectional area of the reinforcement wires 102 in tensionmultiplied by the design yield strength f_(yd).

The reinforcement strip 100 once embedded in mortar has a design bondcapacity F_(bod).

According to the present invention the design yield strength f_(yd) ofthe reinforcement wires 102 and the equivalent diameter d of thereinforcement wires 102 are chosen in such a way that the design valueF_(d) of the reinforcement strip is equal or lower than the bondcapacity F_(bod). It is essential for the reinforcement strip accordingto the present invention that the reinforcement wires are provided witha plurality of ribs.

The diameter of the wire connecting structure 104 is preferably lowerthan 4 mm, for example ranging between 2 and 4 mm, as for example 2.5 mmor 3 mm.

FIG. 2 shows an embodiment of a reinforcement strip 200 according to thepresent invention whereby the wire connecting structure 204 of the stripis provided with protuberances.

The reinforcement strip 200 has two straight, substantially parallelsteel reinforcement wires 202 welded to each other by means of a steelwire connecting structure 204. The welding may be any type of weldingsuch as spot welding or butt welding. The reinforcement wires 202 areprovided with a plurality of ribs 206.

The wire connecting structure 204 runs between the two reinforcementwires 202 along a substantially zig-zag line and is provided withprotuberances 208 protruding at one side from the plane comprising thetwo reinforcement wires 202.

The protuberances 208 are formed by bending some parts of the wireconnecting structure 204 out of the plane formed by the tworeinforcement wires at one side of this plane. It is possible to provideeach length of wire 210 between the reinforcement wires 202 with one ormore protuberance(s) 208.

It is also possible that not all lengths of wire 210 between thereinforcement wires 202 are provided with one or more protuberance(s)208. In the embodiment shown in FIG. 2 there is a protuberance 208 foreach pair of successive steel wire lengths 210.

The protuberances 208 have a certain depth (or height) of for example 1to 6 mm with respect to the plane formed by the upper part of the tworeinforcement wires 202. In this way the protuberances 208 form spacingelements. More preferably the protuberances 208 have a dept (or height)ranging between 1 mm and 4 mm, for example between 2 or 3 mm withrespect to the plane formed by the upper part of the two reinforcementwires 202. In this way the protuberances 208 form spacing elements ordistance holders for the reinforcement strip 200. The protuberancesdefine in this way a certain thickness of the joint between the twoadjacent brick layers which is higher than the total thickness of thereinforcement strip, i.e. the sum of the diameter of the reinforcementwire 202 and the depth (or height) of the protuberances 208 of the wireconnecting structure.

FIG. 3 shows a perspective view of a small part of masonry 320comprising two adjacent layers of bricks 301, 303 and an intermediatejoint 305 of mortar or another adhesive. The joint 305 is reinforced bymeans of a reinforcement strip 300 similar to the reinforcement stripshown in FIG. 2. The reinforcement strip has two reinforcement wires302, each reinforcement wire 302 provided with a plurality of ribs. Thereinforcement wires 302 are connected by a wire connecting structure304. The wire connecting structure 304 is provided with protuberances308.

FIG. 4 shows a cross-section of the embodiment of FIG. 3 along the lineII-II′ in FIG. 3. FIG. 4 shows clearly that each protuberance 308 isdesigned to support on the upper surface of the lower layer 301 ofbricks. It is clear, that by means of the protuberances 308 of the wireconnecting structure 304, the reinforcement wires 302 are situated at adesired or specific distance above the upper surface of the lower layerof bricks 301 and therefore are correctly embedded in the mortar joint305.

The embodiment of reinforcement strip 500 shown in FIG. 5 has a wireconnecting structure 504 having protuberances 508 protruding at bothsides of the plane comprising the two reinforcement wires 502. Theprotuberances 508 are designed to extend upwardly (dashed lines) anddownwardly (full lines) from the plane defined by the two longitudinalreinforcement wires 502. It is again clear, that the reinforcement wires502 are situated at a certain distance above the upper surface of thelower layer 501 of bricks, but also at a certain distance under thelower surface of the upper layer 503 of bricks because the protuberances508 are now designed to contact the upper surface of the lower layer501, as well as the lower surface of the upper layer 503. This meansthat the reinforcement wires 502 are still better embedded in the mortarjoint 503.

A reinforcement strip 500 with both protuberances 508 upward anddownward is very advantageous. First of all it can be placed on anyside, there will always be a gap created both under and above thereinforcement wires 502.

It is important to notice that the function of the reinforcement strip500 according to the present invention is not to keep a fixed andconstant distance between two layers of bricks, as disclosed inUS-A-2004/182029, but to allow the reinforcement wires 502 to becompletely embedded in mortar. A layer of mortar is preferably providedabove the reinforcement strip, under the reinforcement strip or aboveand under the reinforcement strip.

FIG. 6 shows a cross-section through a masonry 620 with still a furtherembodiment of the reinforcement strip 600. The reinforcement strip 600is a ladder-type strip, whereby some steel wires 604 connecting the tworeinforcement wires 602 are bent to form protuberances 608 showing asubstantially crenel-form. In the embodiment shown in FIG. 6 all theundulations or corrugations of the deformed connecting wires 604 havethe same height or depth. It is also possible to deform the steel wireconnecting wires 604 to give these wires 604 a substantially sinusoidalform.

FIG. 7 a shows a cross-section of another embodiment of a reinforcementstrip 700 at a certain location and FIG. 7 b shows a cross-section ofthis another embodiment of a reinforcement strip 700 at anotherlocation. This reinforcement strip 700 is of the ladder type, i.e. theconnecting structure 704 comprises several separate pieces of wire.

The separate pieces of wire are point welded alternatingly above theplane of the reinforcement wires 5 (FIG. 7 a) and under the plane of thereinforcement wires (FIG. 7 b). In case of an upward protuberance 708,the wire piece is point welded above the reinforcement wires 702 (FIG. 7a). In case of a downward protuberance 708′, the wire piece ispoint-welded under the reinforcement wires 702 (FIG. 7 b). Theembodiment of FIG. 7 a and FIG. 7 b has the advantage that the height ordepth of the protuberances can be reduced with the thickness or diameterof the reinforcement wires 702.

FIG. 8 a, FIG. 8 b, and FIG. 8 c all illustrate embodiments of thereinforcement strip 800 where the spacing elements 808′, 808″ arelocated close to the reinforcement wires 802 in order to avoid that thespacing elements fall inside the hollow space of certain bricks.

The embodiment of FIG. 8 a is of a zigzag type reinforcement strip 800.Each piece of connecting wire 804 has two parts 808′ which have beenbent downwards and two parts 808″ which have been bent upwards. Thereason for providing both downwards and upwards bending is that thestrip will provide its spacing function independent of the way it islaid down on the layer of bricks. The spacing elements 808′, 808″ mayeach have a length of 1.5 cm to 2.5 cm in order to provide sufficientstability to the reinforcing strip on the layer of bricks and yet toavoid too much contact between the connecting wires and the layer ofbricks.

The embodiment of FIG. 8 b is also of a zigzag type reinforcement strip800 but here each piece of connecting wire 804 has only one part 808′and one part 808″. Experience has shown that this is sufficient forstability.

The embodiment of FIG. 8 c is of a ladder type. Each piece of connectingwire 804 has two parts 808′ which have been bent downwards and two parts808″ which have been bent upwards.

1. A method to reduce the width of cracks that may be induced inmasonry, said masonry comprising layers of bricks and joints, saidmethod comprising the step of reinforcing at least one joint withreinforcement strips, said reinforcement strips comprising at least twostraight, substantially parallel reinforcement wires connected to eachother by means of a wire connecting structure, said reinforcement wireshave a design yield strength f_(yd) equal or higher than 550/γ_(s) N/mm²and an equivalent diameter d equal or lower than 4 mm, saidreinforcement strip having a resistance F against loads applied on saidreinforcement strip, said resistance F having a design value ofresistance F_(d), said design value F_(d) being equal to thecross-sectional area of the reinforcement wires in tension multiplied bythe design yield strength f_(yd), said reinforcement strip embedded insaid joint having a bond capacity F_(bok), said bond capacity F_(bok)being determined by European Standard EN846-2, said bond capacityF_(bok) having a design bond capacity F_(bod), characterized in thatsaid design yield strength f_(yd) of said reinforcement wires and saiddiameter d of said reinforcement wires being chosen in such a way thatsaid design value F_(d) of said reinforcement strip is equal or lowerthan said design bond capacity F_(bod) of said reinforcement strip andthat said reinforcement wires are provided with a plurality of ribs. 2.A method according to claim 1, wherein said reinforcement wires comprisesteel wires.
 3. A method according to claim 1, wherein said wireconnecting structure comprises a steel wire or a number of steel wires.4. A method according to claim 1, wherein said reinforcement wires areconnected to each other by welding said wire connecting structurebetween two adjacent reinforcement wires.
 5. A method according to claim1, wherein said reinforcement wires have a design yield strength f_(yd)higher than 600/γ_(s) N/mm².
 6. A method according to claim 1, whereinsaid reinforcement wires have an equivalent diameter equal or lower than3.65 mm.
 7. A reinforcement strip comprising at least two straight,substantially parallel reinforcement wires connected to each other bymeans of a wire connecting structure, said reinforcement wires having adesign yield strength f_(yd) equal or higher than 550/γ_(s) N/mm² and anequivalent diameter d equal or lower than 4 mm, said reinforcement striphaving a resistance F against loads applied on said reinforcement strip,said resistance F having a design value of resistance F_(d), said designvalue F_(d) being equal to the cross-sectional area of the reinforcementwires in tension multiplied by the design yield strength f_(yd), saidreinforcement strip embedded in said joint having a bond capacityF_(bok), said bond capacity said bond capacity F_(bok) being determinedby European standard EN846-2, said bond capacity F_(bok) having a designbond capacity F_(bod), characterized in that said design yield strengthf_(yd) of said reinforcement wires and said diameter d of saidreinforcement wires being chosen in such a way that said design valueF_(d) of said reinforcement strip is equal or lower than said designbond capacity F_(bod) of said reinforcement strip and that saidreinforcement wires are provided with a plurality of ribs.
 8. Areinforcement strip according to claim 7, wherein said reinforcementwires comprise steel wires.
 9. A reinforcement strip according to claim7, wherein said wire connecting structure comprises a steel wire or anumber of steel wires.
 10. A reinforcement strip according to claim 7,wherein said reinforcement wires are connected to each other by weldingsaid wire connecting structure between two adjacent reinforcement wires.11. A reinforcement strip according to claim 7, wherein saidreinforcement wires have a design yield strength f_(yd) higher than600/γ_(s) N/mm².
 12. A reinforcement strip according to claim 7, whereinsaid reinforcement wires have an equivalent diameter equal or lower than3.65 mm.
 13. A reinforcement strip according to claim 7, wherein saidwire connecting structure is provided with protuberances protruding fromthe plane comprising said reinforcement wires and forming spacingelements which allow an embedment of said reinforcement wires in mortar.14. A reinforcement strip according to claim 13, wherein saidprotuberances of said wire connecting structure are present at both sideof said plane comprising said reinforcement wires.
 15. Masonrycomprising layers of bricks and joints, whereby at least one joint isreinforced by a number of reinforcement strips as defined in claim 7.